Editing Tritone (section)

== Definitions ==
{{more citations needed section|date=January 2017}}
[[File:Tritone in the chromatic circle.png|thumb|right|Tritone drawn in the [[chromatic circle]].]]
A tritone (abbreviation: ''TT'') is traditionally defined as a musical interval composed of three [[major second|whole tones]]. As the symbol for whole tone is ''T'', this definition may also be written as follows:

: ''TT = T+T+T''

Only if the three tones are of the same size (which is not the case for many [[tuning system]]s) can this formula be simplified to:

: ''TT = 3T''

This definition, however, has two different interpretations (broad and strict).

=== Broad interpretation (chromatic scale) ===
In a [[chromatic scale]], the interval between any note and the previous or next is a semitone. Using the notes of a chromatic scale, each tone can be divided into two semitones:
: ''T = S+S''

For instance, the tone from C to D (in short, C–D) can be decomposed into the two semitones C–C{{Music|sharp}} and C{{Music|sharp}}–D by using the note C{{Music|sharp}}, which in a chromatic scale lies between C and D. This means that, when a chromatic scale is used, a tritone can be also defined as any musical interval spanning six semitones:

: ''TT = T+T+T = S+S+S+S+S+S''.

According to this definition, with the twelve notes of a chromatic scale it is possible to define twelve different tritones, each starting from a different note and ending six notes above it. Although all of them span six semitones, six of them are classified as ''augmented fourth''s, and the other six as ''diminished fifths''.

=== Strict interpretation (diatonic scale) ===
Within a [[diatonic scale]], whole tones are always formed by adjacent notes (such as C and D) and therefore they are regarded as [[incomposite interval]]s. In other words, they cannot be divided into smaller intervals. Consequently, in this context the above-mentioned "decomposition" of the tritone into six semitones is typically not allowed.

If a diatonic scale is used, with its 7 notes it is possible to form only one sequence of three adjacent whole tones (''T+T+T''). This interval is an A4. For instance, in the [[C major]] diatonic scale (C–D–E–F–G–A–B–...), the only tritone is from F to B. It is a tritone because F–G, G–A, and A–B are three adjacent whole tones. It is a ''fourth'' because the notes from F to B are four (F, G, A, B). It is ''augmented'' (i.e., widened) because it is wider than most of the fourths found in the scale (they are [[perfect fourth]]s).

According to this interpretation, the d5 is not a tritone. Indeed, in a diatonic scale, there is only one d5, and this interval does not meet the strict definition of tritone, as it is formed by one semitone, two whole tones, and another semitone:

: ''d5 = S+T+T+S''.

For instance, in the C major diatonic scale, the only d5 is from B to F. It is a ''fifth'' because the notes from B to F are five (B, C, D, E, F). It is ''diminished'' (i.e. narrowed) because it is smaller than most of the fifths found in the scale (they are [[perfect fifth]]s).